This was pretty much the same complaint I had with the NBs. There were way too many loopholes with them turning out to be sisters avenging their dad's death. It was very obvious that this was a sudden and almost overnight decision, going against most things shown about them already. I am also equally disappointed about Om's character change so no comments on that.
If they had actually planned Saumya being grey all along and execute it sensibly with sound reasoning, hell, bring it on. But that is clearly not the case here. And I'd hate to see Saumya being ruined because of that. As it is, they never handled RumYa properly and never showed the whole "fit guy falling for the overweight girl" concept promised. I disliked the silly Romi track so much. God knows what they would do now. Plus, if Soumya also came back to 'avenge her father's death' that would pretty much put her in the same boat as the NBs.
Still, I really hope if they do decide to turn Soumya grey, they give it a proper foundation. If done well, it would turn out to be amazing. And boy would I love to watch it.